As is well known, there are cards with an information storage function. Some of them store information by magnetic stripes and others are "IC cards" including IC memories.
Advantageously, such cards are suitably firmed as "non-contact type information storage cards" and, when compared with magnetic stripe type cards, they can easily be increased in information storage capacity and are highly effective in preventing forgery. It is therefore expected to achieve IC cards having a higher information processing or communication function by incorporating memory chips, CPUs and the like with increased storage capacity into the cards. In the future, it is expected that the IC cards be utilized as telephone cards or tools for carrying information on electronic money.
For example, the non-contact type IC card is a card in which an antenna coil (hereinafter, referred to as a "coil") formed by winding a metallic wire, for example, is electrically connected to an IC chip and buried in the card body made, for example, of plastic, or a card in which a substrate on which an IC chip is placed and an antenna coil is patterned is buried in the card body. In this kind of IC cards, the antenna coil functions as an antenna for transmitting and r(receiving radio waves to and from the outside and also functions as a coil for generating electromotive force to be supplied to the IC chip. Therefore, the IC card of this type has an advantage that incorporation of a power supply such as a battery is not required.
In the future, not only IC cards but such cards that are formed to contain IC chips to provide special functions are required to be increasingly thinner. Then, it can not be expected but that the force caused by a user's handling or the force received from the transportation system of a mechanical card reader causes such thin cards to bend to some extent. A problem in this case is influences on a built-in IC chip when the IC card bends. Since the IC chip is built in the plastic card as described above, stress tends to be caused, when the card bends, at a portion where the IC chip is incorporated. In this case, the IC chip may be stripped out of a prescribed interconnection pattern or the IC chip itself may be damaged. In other words, a power supply path to the IC chip may be cut stopping supply of power, the contents stored in the IC chip may be lost, and so on. That may result in a situation where the properties inherent in IC chips are eliminated. Accordingly, effective protection of the IC chips incorporated in the IC cards is further required as the IC cards are made thinner.
Therefore, by resin molding using dies such as injection molding and transfer molding, a substrate on which an IC chip is placed has been packaged, together with an antenna coil, with a resin so that they form a module. However, the following disadvantages have been caused in the resin packaging process.
Firstly, when a coil is used as an antenna coil and a substrate 2 on which an IC chip 3 is placed is packaged together with the coil with a resin, disadvantages have been caused as described below.
As shown in FIG. 18, when a coil 20A is packaged together with substrate 2 with a resin, coil 20A is housed tog(ether with substrate 2 on which IC chip 3 is placed in a cavity 50 formed by upper and lower dies 5A, 5B so that they surround IC chip 3 and substrate 2. Here, coil 20a is formed by winding a metallic wire around a column-shaped rod, for example, several tens of times to ensure a desired function. Since the formation is carried out by increasing the number of winding times in the thickness direction because it is easy to perform, the thickness has been large. When a melted resin is introduced into cavity 50 through gate 52, therefore, the large thickness of coil 20A blocks the melted resin introduced from gate 52, thus preventing flow of the melted resin in cavity 50. Since the melted resin is relatively viscous, the resin lifts coil 20A upward and forms a flow path in a lower portion of coil 20A, as shown by the arrow, when the melted resin flows in cavity 50. Thus, the melted resin hardly diffuses in the region denoted by the character A and it causes a void and a pinhole. When the resin sets while coil 20A is lifted upward, coil 20A may be exposed from the surface of the resin package or it may easily be exposed, and therefore coil 20A is easily damaged.
Secondly, when an antenna coil formed by patterning copper on substrate 2 formed, for example, of a resin film is adopted as antenna coil 20A and packaged with a resin, disadvantages have been caused as described below.
As shown in FIG. 19, when IC chip 3 is housed together with substrate 2 in cavity 50 so as to package IC chip 3 and substrate 2 with a resin, dies 5 are preheated, and therefore substrate 2 tends to be thermally expanded. Since antenna coil 20 is spirally patterned on substrate 2 using copper which is lower in coefficient of thermal expansion than substrate 2, expansion of substrate 2 is hindered by antenna coil 20 and substrate 2 is warped in a dish shape as a result. When a melted resin is introduced into cavity 50 in this situation, the melted resin flows under the back surface of substrate 2 as shown by the arrow in the drawing. Since the melted resin is relatively viscous, the melted resin which flows under the back surface of substrate 2 may lift substrate 2 upward. If the melted resin sets in this situation, IC chip 3 may be exposed from the surface of the resin package or it may easily be exposed. Thus, IC chip 3 is susceptible to damages.